The ongoing objectives of the immunological-toxicology group include the following interrelated efforts: (1) to evaluate and examine the influence of selected environmental chemicals on the immune response including cellular changes associated with chemical interactions in lymphoreticular cells; (2) to relate alterations in immunological functions with both general toxicity as well as specific organ toxicity; (3) to relate changes in immunological functions with altered host resistance following challenge with either syngeneic tumor cells or infectious agents employing a defined panel of infectivity models; and (4) to refine and validate a panel of immune and host resistance procedures in order to better define immunotoxicity and correlated changes in immune function with altered host resistance. This approach should potentially allow for more accurate assessment of human health risk as well as determine no-effect levels for immunotoxic chemicals.